With the quickly increased demands for all kinds of portable electronic products, such as digital camera, personal digital assistant (PDA), MP3, etc., there are also increasing demands for high-capacity rechargeable batteries that can be fully charged within a largely shortened time with a compact and lightweight charger that has low manufacturing cost and long service life. Most of the currently available battery chargers are CC/CV battery chargers, namely, constant current/constant voltage battery chargers that combine the constant current charging and the constant voltage charging technique to charge batteries or battery packs.
There is also a pulse charging technique that uses constant current to charge batteries and checks the charge voltage status at the battery end, and then increases or decreases a pulse width modulation signal based on the obtained charge voltage status, so as to control and regulate from time to time the output to the batteries during charging. In this manner, it is possible to dynamically adjust the average charge current to the batteries.
However, in the CC/CV charging technique, a large number of detecting points is required, and detecting devices for this purpose must be high-precision to inevitably largely increase the manufacturing cost of the charger. On the other hand, in the pulse charging technique, a highly strict requirement is set for the battery cell protective IC during the course of pulse charging, and the pulse charging circuit is complicate and therefore not convenient for use.
It is therefore tried by the inventor to develop a method of charging batteries to overcome the disadvantages existed in the conventional battery charging techniques, so that a simplified and cost-reduced charging circuit enabling upgraded accuracy of battery charge may be obtained.